This invention relates to trim control of the drive unit on a boat. The basic approach is manual control of the hydraulic motor which adjusts the hydraulic cylinders which adjust the drive unit "in" or "out". There have been proposals for automatic adjustment of the trim angle. These proposals are rather complex in that they take many factors into consideration.
Attention is directed in the following U.S. Pat. Nos.: 3,314,391, 3,834,345, 3,894,250, 4,051,801 and 4,318,699.